1. The invention relates to a process for coring a video signal and particularly to the frequency selective coring of a video signal prior to performing aperture correction.
2. Prior Art
In video processing systems, compromises generally are made when attempting to improve a video detail signal with conventional aperture correction and coring techniques. Coring techniques are used to remove objectionable noise which is emphasized during the aperture correction of the video signal, while optimizing the original shape of the high frequency video detail transitions enhanced by the aperture correction process. Since noise generally increases at the rate of six decibels (db) per octave, the larger quantity of noise exists in the high frequency signal components. Although high frequency noise is not as noticeable to the eye as low frequency noise, the former often is translated when processed, by way of aperture correction, and reappears looking like low frequency noise. The conventional coring techniques core a slice out of the entire signal bandwidth which also removes picture information, particularly at the low frequency end of the spectrum. Typical of such a coring technique is that exemplified in U.S. Pat. No. 3,995,108 to F. Morrison, assigned to the same assignee as this application.
However, use of a coring process after the aperture correction process is, as previously mentioned, a compromise, since it is commonly known that coring the complete detail signal over its entire bandwidth, after aperture correction, generates a loss of low frequency detail information, which is most noticeable during low light levels. Further, the level of coring is compromised since the signal-to-noise ratio when coring after aperture correction is lower than when coring before correction.